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<bibimport/> 
Authors: [[user:Hschwarz|Hans-Jürgen Schwarz]], Nils Mainusch <br>
Authors: [[user:Hschwarz|Hans-Jürgen Schwarz]], Nils Mainusch, NN.... <br>
Translation of the  [http://193.175.110.91/salzwiki/index.php?title=Niter&oldid=11136 German Version] by Hans-Jürgen Schwarz
Translation of the  [http://193.175.110.91/salzwiki/index.php?title=Niter&oldid=11136 German Version] by Hans-Jürgen Schwarz
<br>back to [[Nitrate]]
<br>back to [[Nitrate]]
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|Crystal_System    = orthorhombic
|Crystal_System    = orthorhombic
|Crystal_Structure= orthorhombic - dipyramidal; 2/m 2/m 2/m , see <ref>http://webmineral.com/jpowd/JPX/jpowd.php?target_file=Niter.jpx; Viewed on 15/04/2011</ref>
|Crystal_Structure= orthorhombic - dipyramidal; 2/m 2/m 2/m , see <ref>http://webmineral.com/jpowd/JPX/jpowd.php?target_file=Niter.jpx; Viewed on 15/04/2011</ref>
|Deliqueszenzhumidity=94.6 % (20°C), 93.6% (25°C)
|Deliqueszenzhumidity=93.7 %
|Solubility=315 g/l
|Solubility=3.108 mol/kg
|Density=2.109 g/cm<sup>3</sup>
|Density=2.103 g/cm<sup>3</sup>
|MolVolume=48.04 cm<sup>3</sup>/mol
|MolVolume=48.04 cm<sup>3</sup>/mol
|Molweight =101.11 g/mol
|Molweight =101.10 g/mol
|Transparency =translucent to transparent  
|Transparency =translucent to transparent  
|Cleavage=very good on {001}; good on {010}h<ref>ttp://en.wikipedia.org/wiki/Niter; Viewed on 15/04/2011</ref>
|Cleavage=very good on {001}; good on {010}h<ref>ttp://en.wikipedia.org/wiki/Niter; Viewed on 15/04/2011</ref>
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|Pleochroism=  
|Pleochroism=  
|Dispersion = weak, r < v
|Dispersion = weak, r < v
|Phase_Transition=
|Phase_Transition=  
|chemBehavior=easily soluble in water
|chemBehavior=easily soluble in water
|Comments=
|Comments=
|Literature  = <bib id="Steiger.etal:2014"/> <bib id="Robie.etal:1978"/>
}}
}}
   
   
== Abstract  ==
== Abstract  ==


Niter is one of the most important salts that is responsible for damages of buildings and murals. He is mostly observed indoors, often found in cotton-like efflorescences. Pictures, microphotographs and examples of habits illustrate and complement the description.
Niter is one of the most important salts responsible for damages of building materials and murals. It is mostly observed indoors, often found in cotton-like efflorescence. Pictures, microphotographs and examples of their habits illustrate and complement the description.


== General ==
== General ==


Potassium salts were an important ingredient for the production of gun and explosives in the 19th century, and were both originating from natural sources (potash deposits contain a maximum of 10% KNO<sub>3</sub> among various other potassium salts) and obtained through the transformation of sodium nitrate into potassium chloride. Currently various methods of large-scale production of this salt are based on the reaction between crude potassium salts and nitric acid.
Potassium nitrate was an important ingredient in the production of gun powder and explosives in the 19th century, were obtained from natural sources potash deposits contain a maximum of 10% KNO<sub>3</sub> among various other potassium salts) and obtained through the reaction of sodium nitrate with potassium chloride. Currently various methods of large-scale production of this salt are based on the reaction between crude potassium salts and nitric acid.
<br>Potassium nitrate is also used as a fertilizer in agriculture.<br>
<br>Potassium nitrate is also used as a fertilizer in agriculture.<br>


== Occurrence of Niter  ==
== Occurrence of Niter  ==


Potassium nitrate in natural accumulations can occur anywhere where nitrogen compounds are synthesized in presence of a sufficient quantity of potassium ions (for example during the decomposition of organic matter). Large quantities of nitrifying bacteria and nitrogen compounds are known to be present in manure and urine of living organisms.
Natural accumulations of potassium nitrate can occur anywhere where nitrogen compounds are synthesized in presence of a sufficient quantity of potassium ions (for example during the decomposition of organic matter). Large quantities of nitrifying bacteria and nitrogen compounds are known to be present in manure and urine of living organisms. Large deposits of potassium and sodium nitrate, called "salitre" in Spanish, are found in the desert region of Atacama, nothern Chile, which have been exploited since the 19th century.


== Information on the origin and formation of Niter on monuments  ==
== Information on the origin and formation of Niter on monuments  ==


Contaminated ground water is the major input source of potassium ions in monuments, and nitrates most commonly come from atmospheric pollution. In addition, building and restoration materials can also contain soluble potassium compounds. We can also mention potassium silicate, potassium hydroxide (used as a cleaning agent) and cements.<br>
Contaminated water at the base of monuments is the major input source of both potassium and nitrate ions, the latter having a biogenic origin, such as nitrifying bacteria. These ions will be transported into the material via capillarity. Nitrate ions can also be deposited from atmospheric pollution. Once within the porous system of the material, creep of the formed salt will also contribute to its redistribution. In addition, building and restoration materials can also contain soluble potassium compounds. We can also mention potassium silicate, potassium hydroxide (used as a cleaning agent)and cements.<br>
Nitrates can also originate from biogenic sources and be transported into the material structure via capillary transport of moisture. Microbial activity is an important potential source of nitrates through nitrifying bacteria.


== Solution behavior==
== Solution behavior==


[[file:Loeslichkeit Kaliumnitrat .JPG|400px|thumb|right|'''Figure 1''': Influence of temperature on the water solubility of potassium nitrate in comparison with other damaging salts (after <bib id=Stark.etal:1996/>)]]
[[file:S KNO3.jpg|800px|thumb|left|'''Figure 1''': Solubility of potassium nitrate in water. The molality ''m'' [n(KNO<sub>3</sub>)•kg(H<sub>2</sub>O)<sup>-1</sup>] is plotted versus the temperature.]]
<br clear=all>


Potassium nitrate has a high water solubility, belonging to the group of mobile salts. It can be associated with frequent changes in the accumulation zones in the porous material. The temperature effect on the water solubility is strong, which is reflected in the steep curve in Diagram 1.
Potassium nitrate has a high water solubility, belonging to the group of mobile salts. It can be associated with frequent changes in the accumulation zones in the porous material. The temperature effect on the water solubility is strong, which is reflected in the steep curve in figure 1.


A consequence of this is the danger of solution supersaturation during rapid temperature drop, and a subsequent crystallization of the salt.
A consequence of this is the danger of solution supersaturation during rapid temperature drop, and a subsequent crystallization of the salt.
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<br clear=all>
<br clear=all>
   
   
== Hygroscopicity==
== Hygroscopicity==


[[file:KNO3_a.jpg|thumb|300px|right|'''Figure 2''':Deliqueszenzfeuchten von KNO<sub>3</sub>, Grafik: M. Steiger]]
In the temperature range of 0°C up to 30°C the [[deliquescence humidity]] of potassium nitrate lies always above 90% RH and the temperature dependence is more or less linear. Under the influence of foreign ions the deliquescence humidity is shifted towards lower values.
 
 
[[file:D KNO3 e.jpg|thumb|800px|left|'''Figure 2''':Deliquescence behaviour of potassium nitrate. The water activity ''a<sub>w</sub>'' is plotted versus the temperature.]]
 


Die [[Deliqueszenzfeuchte]] von Kaliumnitrat liegt im Temperaturbereich von 0°C bis 30°C stets über 90% r.F. und ist vergleichsweise linear. Sie wird unter dem Einfluss von Fremdionen allerdings deutlich nach unten verschoben.
<br clear="all">  
<br clear="all">  
{|border="2" cellspacing="0" cellpadding="4" width="70%" align="left" class="wikitable"
{|border="2" cellspacing="0" cellpadding="4" width="70%" align="left" class="wikitable"
|+''Table 1: Deliqueszenzfeuchte von Kaliumnitrat in Temperaturabhängigkeit nach <bib id=Arnold.etal:1991/>''                     
|+''Table 1: Deliquescence humidity of potassium nitrate and its temperature dependence <bib id="Steiger.etal:2014"/>.''                     
|-
|-
|bgcolor = "#F0F0F0" align=center|  '''0°C'''  
|bgcolor = "#F0F0F0" align=center|  '''0°C'''  
|bgcolor = "#F0F0F0" align=center|  '''5°C'''
|bgcolor = "#F0F0F0" align=center|  '''5°C'''
|bgcolor = "#F0F0F0" align=center|  '''10°C'''
|bgcolor = "#F0F0F0" align=center|  '''10°C'''
|bgcolor = "#F0F0F0" align=center|  '''15°C'''
|bgcolor = "#F0F0F0" align=center|  '''20°C'''
|bgcolor = "#F0F0F0" align=center|  '''20°C'''  
|bgcolor = "#F0F0F0" align=center|  '''30°C'''  
|bgcolor = "#F0F0F0" align=center| '''25°C'''  
|bgcolor = "#F0F0F0" align=center| '''40°C'''  
|bgcolor = "#F0F0F0" align=center|  '''30°C'''
 
|-
|-
|bgcolor = "#FFFFEO" align=center| 96.3%r.F.
|bgcolor = "#FFFFEO" align=center| 97.0% RH
|bgcolor = "#FFFFEO" align=center| 96.3%r.F.
|bgcolor = "#FFFFEO" align=center| 95.5% RH
|bgcolor = "#FFFFEO" align=center| 96%r.F.
|bgcolor = "#FFFFEO" align=center| 93.7% RH
|bgcolor = "#FFFFEO" align=center| 95.4%r.F.
|bgcolor = "#FFFFEO" align=center| 91.5% RH
|bgcolor = "#FFFFEO" align=center| 94.6%r.F.
|bgcolor = "#FFFFEO" align=center| 88.9% RH
|bgcolor = "#FFFFEO" align=center| 93.6%r.F.
|bgcolor = "#FFFFEO" align=center| 85.9% RH
|bgcolor = "#FFFFEO" align=center| 92.3%r.F.
 
|}
|}
<br clear="all">  
<br clear="all">  
<!--
{|border="2" cellspacing="0" cellpadding="4" width="70%" align="left" class="wikitable"
{|border="2" cellspacing="0" cellpadding="4" width="70%" align="left" class="wikitable"
|+''Table 2: Deliqueszenzfeuchte bei 21°C im Salzgemisch (Mischungsverhältnis:Gesättigte Lsg. KNO<sub>3</sub>/ gesättigte Lsg.B=1:1) nach <bib id=Vogt.etal:1993/>''  
|+''Table 2: Deliqueszenzfeuchte bei 21°C im Salzgemisch (Mischungsverhältnis:Gesättigte Lsg. KNO<sub>3</sub>/ gesättigte Lsg.B=1:1) nach <bib id="Vogt.etal:1993"/>''  
|-
|-
|bgcolor = "#F0F0F0" align=center|
|bgcolor = "#F0F0F0" align=center|
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{|border="2" cellspacing="0" cellpadding="4" width="40%" align="left" class="wikitable sortable"
{|border="2" cellspacing="0" cellpadding="4" width="40%" align="left" class="wikitable sortable"
|+''Table 3: Moisture sorption Potassium-nitrate in M.% after 56 days storage [after <bib id=Vogt.etal:1993/>]''  
|+''Table 3: Moisture sorption Potassium-nitrate in M.% after 56 days storage [after <bib id="Vogt.etal:1993"/>]''  
|-
|-
|bgcolor = "#F0F0F0"| Storage humidity
|bgcolor = "#F0F0F0"| Storage humidity
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=== Microscopy  ===
=== Microscopy  ===


'''Laboratory Investigations: '''Bei langsamer Rekristallisation eines überwiegend aus Kaliumnitrat bestehenden Präparates werden tafelig-flache, rhombenförmige Kristalle und lattige oder stäbchenförmige Partikel ausgefällt. Insbesondere zu Beginn der Rekristallisation von Kaliumnitrat aus wässerigen Lösungen wie auch aus Lösungen mit geringem Fremdionenanteil, lässt sich eine charakteristische Bildung rhombenförmiger Kristalle beobachten, die am Lösungstropfenrand entstehen. Unter starkem Einfluss von Fremdionen (bei hoher Fremdionenkonzentration im Ausgangsmaterial) können die oben beschriebenen morphologischen Charakteristika nahezu wegfallen, und es treten unspezifischere Kristallformen des Kaliumnitrates auf. Der pH-Wert von überwiegend kaliumnitrathaltigen Präparaten liegt im neutralen Bereich, die Hygroskopizität ist gering.<bib id=Mainusch:2001/><br>
'''Laboratory Investigations: '''Bei langsamer Rekristallisation eines überwiegend aus Kaliumnitrat bestehenden Präparates werden tafelig-flache, rhombenförmige Kristalle und lattige oder stäbchenförmige Partikel ausgefällt. Insbesondere zu Beginn der Rekristallisation von Kaliumnitrat aus wässerigen Lösungen wie auch aus Lösungen mit geringem Fremdionenanteil, lässt sich eine charakteristische Bildung rhombenförmiger Kristalle beobachten, die am Lösungstropfenrand entstehen. Unter starkem Einfluss von Fremdionen (bei hoher Fremdionenkonzentration im Ausgangsmaterial) können die oben beschriebenen morphologischen Charakteristika nahezu wegfallen, und es treten unspezifischere Kristallformen des Kaliumnitrates auf. Der pH-Wert von überwiegend kaliumnitrathaltigen Präparaten liegt im neutralen Bereich, die Hygroskopizität ist gering.<bib id="Mainusch:2001"/><br>


'''Refractive indices:''' &nbsp;&nbsp; n<sub>x</sub> = 1,335; n<sub>y</sub> =1.505; n<sub>z</sub> =1.506<br>'''Birefringnece''':&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Δ = max. 0,171<br>'''Crystal class''':&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; orthorhombic<br>  
'''Refractive indices:''' &nbsp;&nbsp; n<sub>x</sub> = 1,335; n<sub>y</sub> =1.505; n<sub>z</sub> =1.506<br>'''Birefringnece''':&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Δ = max. 0,171<br>'''Crystal class''':&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; orthorhombic<br>  
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<br clear=all>  
<br clear=all>  
   
   
'''Niter in mixed systems''' (after ch <bib id=Mainusch:2001/>)<br>  
'''Niter in mixed systems''' (after ch <bib id="Mainusch:2001"/>)<br>  


Im Mischsystem K<sup>+</sup>-NO<sub>3</sub><sup>2-</sup>– Ca<sup>2+</sup>-SO<sub>4</sub><sup>2- </sup> werden aufgrund des hohen Fremdionenanteils stark verwachsene KNO<sub>3</sub>-Kristalle ausgebildet. Die Tendenz, in großteiligen und länglich geformten Partikeln zu kristallisieren, bleibt beim Kaliumnitrat bestehen. Verfolgt man den Prozess der Rekristallisation, so ist die zeitlich frühere Bildung von Gipskristallen klar nachzuvollziehen. Im vorliegenden, komplexen Mischsystem werden neben Kaliumnitrat und Gips als Hauptkomponenten noch andere Salzphasen wie Kaliumsulfat und Kalium-Calcium-Doppelsalze gebildet (Calciumnitrat konnte nicht festgestellt werden). Der Nachweis aller Salzphasen, die in diesem Mischsystem entstehen können, ist mit einigem Aufwand bei der Trennung und Präparation verbunden. Hilfreich ist es, sich bei der Präparation und der Trennung die Unterschiede der Wasser- und Ethanollöslichkeiten der Salze zunutze zu machen.<br>
Im Mischsystem K<sup>+</sup>-NO<sub>3</sub><sup>2-</sup>– Ca<sup>2+</sup>-SO<sub>4</sub><sup>2- </sup> werden aufgrund des hohen Fremdionenanteils stark verwachsene KNO<sub>3</sub>-Kristalle ausgebildet. Die Tendenz, in großteiligen und länglich geformten Partikeln zu kristallisieren, bleibt beim Kaliumnitrat bestehen. Verfolgt man den Prozess der Rekristallisation, so ist die zeitlich frühere Bildung von Gipskristallen klar nachzuvollziehen. Im vorliegenden, komplexen Mischsystem werden neben Kaliumnitrat und Gips als Hauptkomponenten noch andere Salzphasen wie Kaliumsulfat und Kalium-Calcium-Doppelsalze gebildet (Calciumnitrat konnte nicht festgestellt werden). Der Nachweis aller Salzphasen, die in diesem Mischsystem entstehen können, ist mit einigem Aufwand bei der Trennung und Präparation verbunden. Hilfreich ist es, sich bei der Präparation und der Trennung die Unterschiede der Wasser- und Ethanollöslichkeiten der Salze zunutze zu machen.<br>
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= Dealing with damage caused by Niter  =
= Dealing with damage caused by Niter  =
 
-->


== Niter and damages caused by niter in the image  ==
== Niter and damages caused by niter in the image  ==
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<gallery caption=" " widths="200px" heights="150px" perrow="3">
<gallery caption=" " widths="200px" heights="150px" perrow="3">
Image:KNO3-SalzflaumKoenigslutter.jpg‎| fluffy salt cystals (?)of Niter destroys the surface
Image:KNO3-SalzflaumKoenigslutter.jpg‎| fluffy salt crystals of niter break-up the surface
Image:
Image:
Image:
Image:
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=== Under the polarizing microscope  ===
=== Under the polarizing microscope  ===


<gallery caption="KNO<sub>3</sub> crystallized from aqueous solution on a slide " widths="200px" heights="150px" perrow="3">
<gallery caption="KNO3 crystallized from aqueous solution on a slide" widths="200px" heights="150px" perrow="3">
Image:HJS KNO3 092503-6.jpg | in simple polarized light
Image:HJS KNO3 092503-6.jpg | in simple polarized light
Image:HJS KNO3 092503-5.jpg| under crossed polarizers  
Image:HJS KNO3 092503-5.jpg| under crossed polarizers  
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== Literature  ==
== Literature  ==


<bibprint/>
<biblist/>


[[Category:Niter]]
[[Category:Niter]]
[[Category:Hschwarz]]
[[Category:Schwarz,Hans-Jürgen]]
[[Category:R-MSteiger]]
[[Category:R-MSteiger]]
[[Category:inProgress]]
[[Category:complete]]
[[Category:Nitrate]]
[[Category:Nitrate]]
[[Category:Salt]]
[[Category:Salt]]
[[Category:List]]

Latest revision as of 11:47, 3 May 2023

Authors: Hans-Jürgen Schwarz, Nils Mainusch
Translation of the German Version by Hans-Jürgen Schwarz
back to Nitrate

Niter[1][2][3]
KNO3 I (6)-klein.jpg
Mineralogical name Nitrokalite, Niter, Kalisalpeter
Chemical name Potassium nitrate
Trivial name Saltpetre , Nitrate of potash, Vesta powder, Kali-Salpeter, Kehrsalpeter, Konversionssalpeter
Chemical formula KNO3
Other forms none
Crystal system orthorhombic
Crystal structure orthorhombic - dipyramidal; 2/m 2/m 2/m , see [4]
Deliquescence humidity 20°C 93.7 %
Solubility (g/l) at 20°C 3.108 mol/kg
Density (g/cm³) 2.103 g/cm3
Molar volume 48.04 cm3/mol
Molar weight 101.10 g/mol
Transparency translucent to transparent
Cleavage very good on {001}; good on {010}h[5]
Crystal habit include crusts and acicular crystals formed as efflorescence on cave and mine walls [6]
Twinning
Phase transition
Chemical behavior easily soluble in water
Comments
Crystal Optics
Refractive Indices α = 1.335
β = 1.505
γ = 1.506
Birefringence Δ = 0.171
Optical Orientation biaxial negative
Pleochroism
Dispersion weak, r < v
Used Literature
[Steiger.etal:2014]Title: Weathering and Deterioration
Author: Steiger, Michael; Charola A. Elena; Sterflinger, Katja
Link to Google Scholar
[Robie.etal:1978]Title: Thermodynamic properties of minerals and related substances at 298.15 K and 1 bar pressure and higher temperatures
Author: Robie R.A., Hemingway B.S.; Fisher J.A.
Link to Google Scholar


Abstract[edit]

Niter is one of the most important salts responsible for damages of building materials and murals. It is mostly observed indoors, often found in cotton-like efflorescence. Pictures, microphotographs and examples of their habits illustrate and complement the description.

General[edit]

Potassium nitrate was an important ingredient in the production of gun powder and explosives in the 19th century, were obtained from natural sources potash deposits contain a maximum of 10% KNO3 among various other potassium salts) and obtained through the reaction of sodium nitrate with potassium chloride. Currently various methods of large-scale production of this salt are based on the reaction between crude potassium salts and nitric acid.
Potassium nitrate is also used as a fertilizer in agriculture.

Occurrence of Niter[edit]

Natural accumulations of potassium nitrate can occur anywhere where nitrogen compounds are synthesized in presence of a sufficient quantity of potassium ions (for example during the decomposition of organic matter). Large quantities of nitrifying bacteria and nitrogen compounds are known to be present in manure and urine of living organisms. Large deposits of potassium and sodium nitrate, called "salitre" in Spanish, are found in the desert region of Atacama, nothern Chile, which have been exploited since the 19th century.

Information on the origin and formation of Niter on monuments[edit]

Contaminated water at the base of monuments is the major input source of both potassium and nitrate ions, the latter having a biogenic origin, such as nitrifying bacteria. These ions will be transported into the material via capillarity. Nitrate ions can also be deposited from atmospheric pollution. Once within the porous system of the material, creep of the formed salt will also contribute to its redistribution. In addition, building and restoration materials can also contain soluble potassium compounds. We can also mention potassium silicate, potassium hydroxide (used as a cleaning agent)and cements.

Solution behavior[edit]

Figure 1: Solubility of potassium nitrate in water. The molality m [n(KNO3)•kg(H2O)-1] is plotted versus the temperature.


Potassium nitrate has a high water solubility, belonging to the group of mobile salts. It can be associated with frequent changes in the accumulation zones in the porous material. The temperature effect on the water solubility is strong, which is reflected in the steep curve in figure 1.

A consequence of this is the danger of solution supersaturation during rapid temperature drop, and a subsequent crystallization of the salt.



Hygroscopicity[edit]

In the temperature range of 0°C up to 30°C the deliquescence humidity of potassium nitrate lies always above 90% RH and the temperature dependence is more or less linear. Under the influence of foreign ions the deliquescence humidity is shifted towards lower values.


Figure 2:Deliquescence behaviour of potassium nitrate. The water activity aw is plotted versus the temperature.



Table 1: Deliquescence humidity of potassium nitrate and its temperature dependence [Steiger.etal:2014]Title: Weathering and Deterioration
Author: Steiger, Michael; Charola A. Elena; Sterflinger, Katja
Link to Google Scholar
.
0°C 5°C 10°C 20°C 30°C 40°C
97.0% RH 95.5% RH 93.7% RH 91.5% RH 88.9% RH 85.9% RH



Niter and damages caused by niter in the image[edit]

On objects[edit]


Under the polarizing microscope[edit]



Under the scanning electron microscope[edit]


Weblinks[edit]

Literature[edit]

[Mainusch:2001]Mainusch, Nils (2001): Erstellung einer Materialsammlung zur qualitativen Bestimmung bauschädlicher Salze für Fachleute der Restaurierung, Diplomarbeit, HAWK Hochschule für angewandte Wissenschaft und Kunst Hildesheim/Holzminden/Göttingen, file:Diplomarbeit Nils Mainusch.pdfLink to Google ScholarFulltext link
[Robie.etal:1978]Robie R.A., Hemingway B.S.; Fisher J.A. (1978): Thermodynamic properties of minerals and related substances at 298.15 K and 1 bar pressure and higher temperatures. In: U.S. Geol. Surv. Bull, 1452 ()Link to Google Scholar
[Steiger.etal:2014]Steiger, Michael; Charola A. Elena; Sterflinger, Katja (2014): Weathering and Deterioration. In: Siegesmund S.; Snethlage R. (eds.): Stone in Architecture, Springer Verlag Berlin Heidelberg, 223-316, 10.1007/978-3-642-45155-3_4.Link to Google Scholar
[Vogt.etal:1993]Vogt, R.; Goretzki, Lothar (1993): Der Einfluss hygroskopischer Salze auf die Gleichgewichtsfeuchte und Trocknung anorganischer Baustoffe, unveröffentlichter Bericht.Link to Google Scholar